A variety of prior art manually operated hand-held pump assemblies are well known and used for dispensing a variety of products such as liquids for personal care and pharmaceutical uses, fragrance products and the like. Pumps of this type comprise a housing body and a slidable piston which together define a compression chamber for receiving and dispensing of the product. The body, as well as the internal components contained within the body, are retained by a turret. An inlet in the base of the body communicates, via a dip tube, with the product to be dispensed. A conventional spray actuator communicates with an outlet of the piston to facilitate operation of the pump and provides a mechanical mechanism for dispensing the product, as desired, by an operator.
Directional flow of product to be dispensed, from the interoir of the container into the compression chamber of the body, is controlled by a first one-way valve, typically located at or adjacent to the coupling of the body inlet to the dip tube. A second one-way valve enables the product to be dispensed from the compression chamber through the piston outlet and into a supply passage of the actuator. Finally, the product is dispensed out through a discharge orifice of the actuator.
It is desirable for the pump to reach a specified pressure, prior to releasing the product to be dispensed from the compression chamber, to ensure that the product dispensed out the discharge orifice exhibits consistent and uniform spray characteristics. For example, some sprays need to consist of particles of uniform size, e.g. particles lying within a narrow particle size range, in order for proper dispensing of the product. It is also desirable to dispense a specific dosage of product during a single actuation of the actuator. To accomplish both the desired dosage and particle size requirements, the construction and function of the pump assembly require accurately designed internal components which must be precisely controlled during operation of the pump assembly. Because the body, the piston, the spring, the valve, etc., determine the configuration and operating pressure of the compression chamber, these components are very important in controlling the function of the pump assembly.
Product dispensing requirements are increasingly more demanding. With an increase in the use of low volatile solvents, as the main carrier component for the product to be dispensed, and as well as using more viscous gel-type liquids, the design requirements for dispensing such products are more critical. In particular, the low volatile solvents and the viscous gel-type liquids require higher discharge pressures, to facilitate proper dispensing thereof, versus products that include solvents which are readily converted into vapor upon discharge. In an attempt to overcome this problem and facilitate control of the resulting spray configuration, many prior art pump assemblies use a single spring to both actuate the piston and also bias a second one-way valve. This single spring forces the piston back into its initial static position, once the actuator has actuated the piston, and holds the second one-way valve closed until a desired operating pressure is reached.
Other prior art designs use a first spring for returning the piston and a second spring for biasing the second one-way valve independently of the piston. The intended advantage of the two spring arrangement is that the second one-way valve spring can be independently adjusted to facilitate opening of the piston valve at a desired operating pressure. In either case, the second one-way valve and the spring(s) are all contained within the compression chamber of the body and are subjected to the generated operating pressure within the compression chamber. The spring(s) (or other known conventional biasing members) are typically located to bias the second one-way valve against a piston valve seat. The amount of pressure required to compress the spring, and thus move the second one-way valve away from its associated valve seat, determines the operating pressure of the pump assembly. The construction of the spring thus determines the pressure at which the product is displaced from the body out through the discharge orifice. The spring pressure translates into a high reaction force upon the product as it is released by the second one-way valve and overcomes the spring bias.
It is to be appreciated that in order for the pump assembly to dispense liquid properly, the pump section of the assembly must be initially purged of any air contained within the compression chamber-this initial purging step is commonly referred to as "priming" of the pump. When the actuator is initially depressed by an operator, any air contained within the compression chamber of the body must be displaced in order for product to be siphoned into the compression chamber of the body via the dip tube. By depressing the actuator, the piston is moved toward a base of the body thereby compressing the spring as well as any air contained within the compression chamber. The compressed air assists with maintaining the first one-way valve in a closed position. The compressed air also induces an opening force on the second one-way valve but, in most cases, the induced force of the compressed air may never reach a high enough pressure to overcome the spring closing force of the second one-way valve. For this reason, prior art pumps use a small rib(s), or some other mechanical device located near the end of the compression stroke, to disrupt the seal between an inner part of the body and the piston and allow the compressed air to escape from the compression chamber. Two methods are used for allowing the compressed air to escape from the compression chamber. The first method is to allow the air to escape around the piston which can result in residual product drying along the escape path and seizing the piston. The second method is to allow air to escape down the dip tube which results in the air and the product to be dispensed reciprocating back and forth within the tube, which is also undesirable.
Because both the second one-way valve and the spring occupy space inside the body, these components effect the compression of the air during the priming operation of the pump, and thus effect the operation of the second one-way valve. This also means that the product, siphoned via the dip tube into the body, is then pushed back through the system in the reverse direction as the piston reciprocates. This to and for movement of the air and the product reduces the efficiency of the pump and increases the force needed to operate the system. In addition, the number of strokes required in order to remove the air contained within the compression chamber is increased.